Warming study indicates water problems in the West

November 21, 2002

Accelerated Climate Prediction Initiative

"Water may be the resource that defines the limits of sustainable development," states a 2001 United Nations Population Fund report, which noted that water use has grown six-fold over the past 70 years.

Nowhere is that more true than in the western United States, where existing water resources already are stretched to their limits. There is little or no leeway for changes in current water allocations. But there is every reason to expect that climate change, such as that associated with greenhouse warming, could dramatically alter the availability of water in the West. In the most rigorous study to date of potential greenhouse impacts, leading scientists detail how major water problems could evolve over the next 50 years throughout the West as a result of climate change already underway.

Many people have heard about the impacts of global warming, but the general public typically doesn't grasp the ramifications of such changes. A degree or so change in global mean temperature seems harmless enough. What most people do not know is that the regional or local climate changes associated with global warming will be far more significant than apparently small average changes might imply.

New simulations by a group of leading global warming and climate change researchers suggest the effects of rising temperatures will exacerbate problems we are beginning to see. In the West, the effects of global warming already have begun to emerge in earlier melting of mountain snow packs and spring flooding dates. Scientific studies show that these, and other expected climate changes, could have a devastating impact on water resources in some parts of the West over the next half century.

For instance:"Population and economic growth already are placing severe pressure on water resources in the West. Climate change is one more very important factor that has to be taken into account when thinking about the future," said Bill Pennell, director of the Atmospheric Science and Global Change Division at Pacific Northwest National Laboratory.

"It also is important to point out," said Dennis Lettenmaier, Professor of Civil Engineering at the University of Washington, "that these predictions are based on one of the most conservative climate models. Other models show a much larger warming effect. However, even this conservative model indicates substantial changes. For example, by mid-century the yearly average snow pack in the Washington and Oregon Cascades may be reduced on the order of 50 percent and because most of our water storage is in this snow pack, such a reduction will result in big changes in flows and water temperatures in Cascade rivers and streams."
Acknowledgment of Participants
The ACPI Pilot effort was supported largely by the Department of Energy's Office of Biological and Environmental Research through numerous contracts and subcontracts to the participants. The production runs of global and regional models were largely accomplished with resources from the Center for Computational Sciences at Oak Ridge National Laboratory, which is supported by DOE's Office of Science. The San Diego Supercomputer Center provided dedicated machine resources for the ocean initialization component of the ACPI Pilot. Ocean data was provided by Estimating the Circulation and Climate of the Ocean, or ECCO. Los Alamos National Laboratory provided computer resources for PCM work and additional feasibility tests associated with the ocean initialization. In addition to DOE support, many of the participating organizations also supported the effort, including Scripps Institution of Oceanography, U.S. Geological Survey, Department of Defense, National Center for Atmospheric Research, University of Washington and Pacific Northwest National Laboratory.

Additional Contact:
Rob Harrill
University of Washington
(206) 543-2580

DOE/Pacific Northwest National Laboratory

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